This invention relates to a clamping apparatus for locking a tool against the interior walls of a well, chimney, or similar conduit structure.
Tools of various kinds are frequently lowered into oil and gas wells. A tool often carries one or more instrument packages configured to provide data about a well. Precise measurement of these data often requires that the instruments be rigidly held in a fixed position relative to the well. Sometimes, as in the case of geophones used to obtain a seismic survey of a geological formation, the instruments must be rigidly held against the casing walls of the well to achieve optimum seismic coupling between the instruments and the formation.
Many prior locking devices relied on the weight of the tool components to provide locking force. Some seismic survey techniques, however, and particularly some recently developed techniques, call for a tighter lock against the casing wall than can be provided by tool weight alone. A locking force of three to four times that of the tool weight is often desirable.
A simple way of generating a locking force, and one very commonly used in the art, is to directly couple a motor and a spring to a clamping arm. This approach is limited by the force that can be generated by the motor and by the time required for motor movement in locking and unlocking the tool.
The time limitation can be particularly significant when the tool must be lowered to a series of positions in the well to obtain a profile of the geological formation. The locking and unlocking operations can slow down completion of the profile and add to the cost of exploration.